mysql - 从表中选择具有重复字段的行，但优先考虑分组依据

Question

包含列 id、order_number、位置的表格 数据看起来像

[1, 123, 'texas']
[2, 123, 'ny']
[3, 456, 'texas']
[4, 456, 'ny']
[5, 678, 'hawaii']

我想选择来自 ny 且与 texas 具有相同 order_number 的记录的 id >

Answer 1

一种选择是使用 EXISTS 子句:

SELECT id
FROM yourTable t1
WHERE location = 'ny' AND EXISTS (SELECT 1 FROM yourTable t2
                                  WHERE t1.order_number = t2.order_number AND
                                        t2.location = 'texas');

编辑:如果您想使用聚合方法，那也是可能的:

SELECT MAX(CASE WHEN location = 'ny' THEN id END) AS id
FROM yourTable
WHERE location IN ('ny', 'texas')
GROUP BY order_number
HAVING COUNT(DISTINCT location) = 2;

Demo

在这里，我们可以按 order_number 进行聚合，然后转出纽约的 id 值。